Actively exploited vulnerability
ASUS Routers: authentication bypass flaw under attack
CVE-2021-32030 · ASUS Routers Improper Authentication Vulnerability
What is affected
ASUS Routers are the kind of equipment many homes and small offices run for years without touching: a router, camera or storage box. Attackers scan the internet for exposed units, and a hijacked one can spy on traffic or be enrolled in a botnet without any visible sign.
ASUS Lyra Mini and ASUS GT-AC2900 devices contain an improper authentication vulnerability that allows an attacker to gain unauthorized access to the administrative interface. The impacted products could be end-of-life (EoL) and/or end-of-service (EoS). Users should discontinue product utilization.
What an attacker can do
This is a authentication bypass flaw. It lets an attacker get in without a valid username and password and act as a legitimate user, often as an administrator.
- How it is reached
- Over the internet or network
- Access the attacker needs
- No account needed
- Does the victim have to do something?
- No, works without the victim doing anything
What to do
- Check whether you own this device: look at the label on your router, camera or NAS, or open its admin page and note the model and firmware version.
- Install the latest firmware from the manufacturer's support page or the device's own update menu.
- If the manufacturer no longer releases updates for the model, replace it. An end-of-life device with an exploited flaw cannot be made safe.
- Turn off remote administration from the internet unless you truly need it, and change the default admin password.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Vendor advisories and fixes
How urgent is it
CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on June 2, 2025, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by June 23, 2025, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.
The EPSS model estimates a 99% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.9% of all scored vulnerabilities.
Its CVSS severity score is 9.8 out of 10 (critical), as recorded in the US National Vulnerability Database.
Technical description
The administrator application on ASUS GT-AC2900 devices before 3.0.0.4.386.42643 and Lyra Mini before 3.0.0.4_384_46630 allows authentication bypass when processing remote input from an unauthenticated user, leading to unauthorized access to the administrator interface. This relates to handle_request in router/httpd/httpd.c and auth_check in web_hook.o. An attacker-supplied value of '\0' matches the device's default value of '\0' in some situations. Note: All versions of Lyra Mini and earlier which are unsupported (End-of-Life, EOL) are also affected by this vulnerability, Consumers can mitigate this vulnerability by disabling the remote access features from WAN.